Dibekacin derivatives and arbekacin derivatives active against resistant bacteria, and the production thereof

ABSTRACT

As new dibekacin derivatives and new arbekacin derivatives are now provided 2&#34;-amino-2&#34;-deoxydibekacin, 2&#34;-amino-5,2&#34;-dideoxydibekacin, 2&#34;-amino-2&#34;-deoxyarbekacin, 2&#34;-amino-5,2&#34;-dideoxyarbekacin, 2&#34;-amino-5,2&#34;-dideoxy-5-epi-fluoroarbekacin and 2&#34;-amino-5,2&#34;-dideoxy-5-epi-aminoarbekacin which all exhibit high antibacterial activity against a wide variety of gram-positive and gram-negative bacteria, including resistant bacteria such as methicillin-resistant Staphylococcus aureus and which are of low toxicity to mammals and are useful as antibacterial agent for treatment of bacterial infections.

This is a division of application Ser. No. 08/154,002 filed Nov. 18,1993 now U.S. Pat. No. 5,988,038.

FIELD OF THE INVENTION

This invention relates to new compounds, 2"-amino-2"-deoxydibekacin and2"-amino-2"-deoxyarbekacin as well as their 5-deoxy derivatives whichare active against a wide variety of gram-positive and gram-negativebacteria and also against resistant bacteria, including resistantstrains of Staphylococcus aureus. This invention also relates to anothernew compounds, 2"-amino-5,2"-dideoxy-5-epi-fluoro-arbekacin and2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin which are active against awide variety of gram-positive and gram-negative bacteria and alsoagainst resistant bacteria, including resistant strains ofStaphylococcus aureus. These new compounds are of low toxicity and areuseful as chemotherapeutic agent for therapeutic treatment of bacterialinfections. This invention further relates to processes for thepreparation of the above-mentioned new compounds. This invention furtherincludes an antibacterial or a pharmaceutical composition comprising oneof these new compounds as active ingredient.

BACKGROUND OF THE INVENTION

In 1967, the present inventors, and their associators investigated theresistance mechanism of resistant bacteria against some aminoglycosidicantibiotics such as streptomycin and kanamycins which were used widelyas chemotherapeutic agents towards 1967, and elucidated for the firsttime the resistance mechanism such that these antibiotics can beinactivated by the action of various modifying enzymes as produced bythe resistant bacteria. Then, further investigations were conducted,where a variety of kanamycin derivatives which cannot be inactivated bythese modifying enzymes were synthetically prepared. Some sucesses werethen obtained in proving the resistance mechanism of resistant bacteriaagainst such kanamycin derivatives and also providing such variouskanamycin derivatives which are actually useful as chemotherapeuticagents for bacterial infections [see, H. Umezawa and S. Kondo:"Aminoglycoside Antibiotics" edited by H. Umezawa and I. R. Hooper,Springer-Verlag, Berlin, Heidelberg, New York, page 267 (1982); and S.Kondo: "Biochemistry of Drug Resistance Mechanism", edited by S.Mitsuhashi, published by Gakkai Publishing Center, page 27 (1981)].

Amongst these kanamycin derivatives, 3',4'-dideoxykanamycin B, i.e.dibekacin [H. Umezawa et al., "J. Antibiotics", 24, 485 (1971)] has beenused widely as chemotherapeutic agent active against drug-resistantbacteria since 1975. On the other hand,(S)-1-N-(4-amino2-hydroxybutyryl)dibekacin, i.e. arbekacin [S. Kondo etal., "J. Antibiotics", 26, 412, (1973)] has been used as a specificmedicine for treating infections with methicillin-resistantStaphylococcus aureus (MRSA) since the end of 1990.

In the meanwhile, there was known only one compound named seldomycinfactor-5 as such an aminoglycosidic antibiotic which containsdeoxystreptamine whose 2"- and 3"-positions each bear an amino group andwhich has the following formula (A): ##STR1## Seldomycin factor-5 isproduced by Streptomyces hofunensis [J. B. McAlpine et al., "J.Antibiotics", 30, 39 (1977)], but this antibiotic compound is clearlydifferent in its chemical structure and antibacterial activity from thenew 2"-amino-2"-deoxy derivatives of dibekacin and arbekacin nowprovided according to this invention.

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) hasbrought about such a serious trouble that this bacterial strain rapidlypropagated through hospital infections, leading to very seriousinfectious diseases. Thus the development of effectively usabletherapeutic agents therefor is being earnestly wanted. Arbekacin has nowbeen used for more than one year, but there has appeared yet noarbekacin-resistant strain of MRSA (which will show a minimum growthinhibitory concentration of arbekacin of not less than 25 μg/ml), inclinics. Since, however, there has been found the presence of such astrain of MRSA which exhibits a moderate resistance to arbekacin (withshowing a minimum growth inhibitory concentration of arbekacin between6.25-12.5 μg/ml), we, the present inventors, have investigated detaildlythe resistance mechanism of the MRSA strain having the moderateresistance to arbekacin. As a result, we have affirmed that theresistance mechanism of MRSA to arbekacin is due primarily to anenzymatic inactivation of arbekacin by phosphorylation of the 2"-OHgroup of arbekacin.

Based on these findings, we have further proceeded our study with theintention of synthesizing such novel derivatives of dibekacin orarbekacin which are not or little susceptible of the enzymaticphosphorylation. Thus, an object of this invention is to provide newdibekacin or arbekacin derivatives which are obtainable from dibekacinthrough chemical syntheses, which have broad and effective antibacterialactivities not only against MRSA, but also against gram-positive andgram-negative bacteria, and which are of low toxicity.

DETAILED DESCRIPTION OF THE INVENTION

We have now succeeded, as a result of these investigations, insynthesizing novel arbekacin derivatives which have such structure thatthe 2"-hydroxyl group of arbekacin susceptible of being phosphorylatedhas been converted into an amino group, namely,2"-amino-2"-deoxyarbekacin and 2"-amino-5,2"-dideoxyarbekacinrepresented by the undermentioned general formula (I). And, we have alsosucceeded in synthesizing novel dibekacin derivatives which have suchstructure that the 2"-hydroxyl group of dibekacin has been convertedinto an amino group, namely, 2"-amino-2"-deoxydibekacin and2"-amino-5,2"-dideoxydibekacin represented by the undermentioned generalformula (II). We have further found that the above-mentioned novel twoarbekacin derivatives and novel two dibekacin derivatives thussynthesized not only strongly inhibit the growth ofmethicillin-resistant Staphylococcus aureus (MRSA), but also exhibitbroad and effective antibacterial activities against gram-positive andgram-negative bacteria, with having low toxicity to mammals.

According to a first aspect of this invention, therefore, there areprovided 2"-amino-2"-deoxyarbekacin or 5-deoxy derivative thereofrepresented by the following general formula (I) ##STR2## wherein Rmeans a hydroxyl group or a hydrogen atom, and an acid addition saltthereof.

The compound of general formula (I) where R means a hydroxyl group is2"-amino-2"-deoxyarbekacin represented by the following formula (Ia)##STR3##

The compound of general formula (I) where R means a hydrogen atom is2"-amino-5,2"-dideoxyarbekacin represented by the following formula (Ib)##STR4##

Further, according to a second aspect of this invention, there areprovided 2"-amino-2"-deoxydibekacin or 5-deoxy derivative thereofrepresented by the following general formula (II) ##STR5## wherein Rmeans a hydroxyl group or a hydrogen atom, and an acid addition saltthereof.

The compound of general formula (II) where R means a hydroxyl group is2"-amino-2"-deoxydibekacin represented by the following formula (IIa)##STR6##

The compound of general formula (II) where R means a hydrogen atomis2"-amino-5,2"-dideoxydibekacin represented by the following formula(IIb) ##STR7##

Physico-chemical properties of the new 2"-amino-2"-deoxy derivatives ofarbekacin and dibekacin and their 5-deoxy derivatives having generalformula (I) and (II), respectively, as obtained according to thisinvention are described below:

[1] 2"-Amino-2"-deoxyarbekacin [Compound Ia]

(1) Color and form: colorless powder

(2) Molecular formula: C₂₂ H₄₅ N₇ O₉

(3) Mass spectrum(SI-MS): m/z 552(M+H)³⁰

(4) Melting point: 155°-160° C. (decomposed)

(5) Optical rotation: [α]_(D) ²⁰ +86° (e 0.53, H₂ O)

(6) UV and visible ray-absorption spectra: no specific absorption

(7) Infrared absorption spectrum: 3380, 2930, 1650, 1580, 1470, 1380,1320, 1100, 1020 cm⁻¹

(8) ¹ H-NMR spectrum(D₂ O, pD 2): as shown in TABLE 1 hereinafter

(9) ¹³ C-NMR spectrum(D₂ O, pD 2): as shown in TABLE 2 hereinafter

(10) Solubility: easily soluble in water

(11) Distinction between basic, acidic and neutral substances in nature:basic substance

[2] 2"-Amino-5,2"-dideoxyarbekacin [Compound Ib]

(1) Color and form: colorless powder

(2) Molecular formula; C₂₂ H₄₅ N₇ O₈

(3) Mass spectrum(FD-MS): m/z 536(M+H)⁺

(4) Melting point: 196°-198° C. (decomposed)

(5) Optical rotation: [α]_(D) ²⁰ +92° (c 0.74, H₂ O)

(6) UV and visible ray-absorption spectra: no specific absorption

(7) Infrared absorption spectrum: 3400, 2940, 1650, 1580, 1460, 1390,1340, 1040 cm⁻¹

(8) ¹ H-NMR spectrum(D₂ O, pD 2): as shown in TABLE 1 hereinafter

(9) ¹³ C-NMR spectrum(D₂ O, pD 2): as shown in TABLE 2 hereinafter

(10) Solubility: easily soluble in water

(11) Distinction between basic, acidic and neutral substances in nature:basic substance

[3] 2"-Amino-2"-deoxydibekacin [Compound IIa]

(1) Color and form: colorless powder

(2) Molecular formula; C₁₈ H₃₈ N₆ O₇

(3) Mass spectrum(SI-MS): m/z 451(M+H)⁺

(4) Melting point: 129°-133° C. (decomposed)

(5) Optical rotation: [α]_(D) ²⁰ +122° (c 0.39, H₂ O)

(6) UV and visible ray-absorption spectra: no specific absorption

(7) Infrared absorption spectrum: 3350, 2930, 1580, 1480, 1380, 1340,1120, 1020 cm⁻¹

(8) ¹ H-NMR spectrum(D₂ O, pD 2): as shown in TABLE 1 hereinafter

(9) ¹³ C-NMR spectrum(D₂ O, pD 2): as shown in TABLE 2 hereinafter

(10) Solubility: easily soluble in water

(11) Distinction between basic, acidic and neutral substances in nature:basic substance

[4] 2"-Amino-5,2"-dideoxydibekacin [Compound IIb]

(1) Color and form: colorless powder

(2) Molecular formula: C₁₈ H₃₈ N₆ O₆

(3) Mass spectrum(SI-MS): m/z 435(M+H)⁺

(4) Melting point: 129°-131° C. (decomposed)

(5) Optical rotation: [α]_(D) ²⁰ +166° (c 0.51, H₂ O)

(6) UV and visible ray-absorption spectra: no specific absorption

(7) Infrared absorption spectrum: 3350, 2940, 1590, 1460, 1380, 1340,1100, 1020 cm⁻¹

(8) ¹ H-NMR spectrum(D₂ O, pD 2): as shown in TABLE 1 hereinafter

(9) ¹³ C-NMR spectrum(D₂ O, pd 2): as shown in TABLE 2 hereinafter

(10) Solubility: easily soluble in water

(11) Distinction between basic, acidic and neutral substances in nature:basic substance

                  TABLE 1                                                         ______________________________________                                        Chemical Shift in deutero-water                                               (pD 2) (ppm*)                                                                       Compound             Compound                                           Proton                                                                              Ia        Compound Ib                                                                              IIa     Compound IIb                               ______________________________________                                        1-H   4.20   ddd    4.08 m     3.79 m    3.70  m                              2-H.sub.ax                                                                          1.98   ddd    1.79 ddd   2.18 ddd  1.96  ddd                            2-H.sub.eq                                                                          2.33   ddd    2.34 ddd   2.58 ddd  2.58  ddd                            3-H   3.58   ddd    3.52 ddd   3.64 ddd  3.60  ddd                            4-H   4.06   dd     4.06 m     4.19 m    4.11  ddd                            5-H.sub.ax                                                                          3.95   dd     1.72 ddd   4.18 m    1.76  ddd                            5-H.sub.eq          3.00 ddd             3.21  ddd                            6-H   4.13   dd     4.09 m     4.15 dd   4.17  ddd                            1'-H  5.82   d      5.39 d     5.76 d    5.40  d                              2'-H  3.62   ddd    3.57 ddd   3.59 ddd  3.57  ddd                            3'-H.sub.2                                                                          2.08   m      2.04 m     2.04 m    2.05  m                              4'-H.sub.ax                                                                         1.67   dddd   1.59 m     1.64 dddd 1.62  m                              4'-H.sub.eq                                                                         1.99   m      1.90 m     1.95 m    1.92  m                              5'-H  4.24   m      4.06 m     4.22 m    4.08  m                              6'-H.sub.2                                                                          3.17   dd     3.08 dd    3.14 dd   3.10  dd                                   3.32   dd     3.26 dd    3.28 dd   3.28  dd                             1"-H  5.52   d      5.45 d     5.72 d    5.55  d                              2"-H  3.86   m      3.84 dd    3.98 dd   3.80  dd                             3"-H  3.87   m      3.74 dd    3.87 dd   3.72  m                              4"-H  3.86   m      3.69 dd    3.80 dd   3.71  m                              5"-H  4.13   m      3.95 m     4.18 m    3.98  m                              6"-H.sub.2                                                                          3.88   dd     3.75 dd    3.79 dd   3.76  dd                                   3.93   dd     3.96 m     3.98 dd   3.96  dd                             2"'-H 4.37   dd     4.33 dd                                                   3"'-H.sub.2                                                                         2.01   m      1.94 dddd                                                       2.22   ddt    2.19 dddd                                                 4"'-H.sub.2                                                                         3.22   t      3.17 m                                                    ______________________________________                                         *Sodium trimethylsilylpropionate was deemed as giving 0 ppm.             

                  TABLE 2                                                         ______________________________________                                        Chemical shift in deutero-water                                               (pD 2) (ppm*)                                                                       Compound             Compound                                           Carbon                                                                              Ia        Compound Ib                                                                              IIa     Compound IIb                               ______________________________________                                        1     50.1   d      51.6  d    49.7 d    51.6  d                              2     31.1   t      31.0  t    29.1 t    29.2  t                              3     49.4   d      52.0  d    48.9 d    51.5  d                              4     78.2   d      71.2  d    78.3 d    70.9  d                              5     75.0   d      33.9  t    74.6 d    33.0  t                              6     78.3   d      77.9  d    81.8 d    78.3  d                              1'    96.0   d      90.7  d    96.3 d    90.8  d                              2'    49.6   d      48.9  d    49.6 d    48.8  d                              3'    21.3   t      21.7  t    21.3 t    21.6  t                              4'    26.2   t      26.3  t    26.1 t    26.2  t                              5'    66.8   d      66.4  d    67.0 d    66.5  d                              6'    43.4   t      43.4  t    43.3 t    43.3  t                              1"    93.8   d      96.3  d    94.6 d    96.9  d                              2"    51.7   d      51.6  d    51.7 d    51.8  d                              3"    53.0   d      52.9  d    52.8 d    53.1  d                              4"    65.8   d      66.4  d    66.3 d    66.6  d                              5"    72.8   d      73.1  d    73.8 d    73.1  d                              6"    60.4   t      61.2  t    60.8 t    61.2  t                              1'"   176.4  s      176.3 s                                                   2'"   70.3   d      70.2  d                                                   3'"   31.5   t      31.7  t                                                   4'"   37.6   t      37.6  t                                                   ______________________________________                                         *Dioxane (67.4 ppm) was used as internal standard.                       

Acid addition salts of 2"-amino-2"-deoxyarbekacin and2"-amino-5,2"-dideoxyarbekacin having general formula (I) and of2"-amino-2"-deoxydibekacin and 2"-amino-5,2"-dideoxydibekacin havinggeneral formula (II) according to this invention include such those withpharmaceutically acceptable inorganic acids such as hydrochloric acid,sulfuric acid, phosphoric acid, nitric acid, etc. and such those withpharmaceutically acceptable organic acids such as malic acid, citricacid, ascorbic acid, methanesulfonic acid, etc.

Biological properties of the new 2"-amino-2"-deoxy derivatives ofdibekacin and arbekacin, and their 5-deoxy derivatives obtainedaccording to this invention are described below:

(1) Antibacterial activities

Minimum growth inhibitory concentrations (MIC) of each of2"-amino-2"-deoxyarbekacin (Compound Ia), 2"-amino-5,2"-dideoxyarbekacin(Compound Ib), 2"-amino-2"-deoxydibekacin (Compound IIa) and2"-amino-5,2"-dideoxydibekacin (Compound IIb) against various bacteria(20 strains) and against clinically isolated strains of MRSA (50strains) were determined by standard serial dilution method onMuller-Hinton's agar medium (as estimated after cultivating at 27° C.for 18 hours), and the test results obtained are shown in TABLE 3 andTABLE 4, respectively.

                  TABLE 3                                                         ______________________________________                                                       MIC. (μg/ml)                                                                 Com-    Com-    Com-  Com-                                                    pound   pound   pound pound                                  Test organisms   Ia      Ib      IIa   IIb                                    ______________________________________                                        Staphylococcus aureus                                                                          0.39    ≦0.20                                                                          0.78  0.39                                   FDA209P                                                                       S. aureus Smith  ≦0.20                                                                          ≦0.20                                                                          0.39  ≦0.20                           S. epidermidis 109                                                                             0.78    0.39    1.56  0.78                                   Bacillus subtilis PCI219                                                                       0.20    ≦0.20                                                                          ≦0.20                                                                        ≦0.20                           B. cereus ATCC10702                                                                            3.13    0.78    3.13  1.56                                   Escherichia coli NIHJ                                                                          0.78    0.39    0.78  1.56                                   E. coli K-12 ML1629                                                                            3.13    1.56    3.13  6.25                                   E. coli K-12 ML1410                                                                            1.56    1.56    1.56  3.13                                   E. coli K-12 LA290 R55                                                                         0.78    0.78    1.56  3.13                                   E. coli JR66/W677                                                                              3.13    3.13    3.13  6.25                                   Klebsiella pneumoniae PCI602                                                                   1.56    0.78    3.13  3.13                                   Shigella dysenteriae JSI1910                                                                   3.13    1.56    3.13  6.25                                   Salmonella typhi T-63                                                                          0.78    0.78    1.56  3.13                                   Proteus vulgaris OX19                                                                          1.56    0.78    1.56  1.56                                   Providencia rettgeri GN311                                                                     1.56    0.78    1.56  1.56                                   Serratia marcescens                                                                            3.13    6.25    12.5  25                                     Pseudomonas aeruginosa A3                                                                      1.56    0.39    1.56  0.78                                   P. aeruginosa H9 6.25    3.13    6.25  12.5                                   P. aeruginosa TI-13                                                                            3.13    1.56    3.13  3.13                                   P. aeruginosa PST1                                                                             12.5    6.25    50    100                                    ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                                   Antibacterial MIC spectra                                                     (μg/ml) against 50 clinically                                   Test compound                                                                            isolated strains of MRSA                                                                        MIC.sub.50                                                                            MIC.sub.90                               ______________________________________                                        Compound Ia                                                                              0.20-3.13         0.78    1.56                                     Compound Ib                                                                              0.20-3.13         0.78    1.56                                     Compound IIa                                                                             ≦0.20-50   6.25    25                                       Compound IIb                                                                             0.78-25           3.13    25                                       DKB        ≦0.20->100 50      >100                                     (comparative)                                                                 ABK        ≦0.20-6.25 0.39    6.25                                     (comparative)                                                                 ______________________________________                                         Note:- MIC.sub.50 or MIC.sub.90 represents the concentration of tested        active compound at which 50% or 90% of the total numbers of the bacterial     strains tested were inhibited from their growth. DKB denotes dibekacin,       and ABK denotes arbekacin.                                               

(2) Acute toxicity

50% Lethal dosages (LD₅₀, observations for two weeks) of the newcompounds of this invention as estimated upon single intravenousadministration to mice (ICR-strain, 4 weeks old, female) are as follows:

    ______________________________________                                                               LD.sub.50                                              ______________________________________                                        2"-Amino-2"-deoxyarbekacin (Compound Ia)                                                               >100    mg/kg                                        2"-Amino-5,2"-dideoxyarbekacin (Compound Ib)                                                           50-100  mg/kg                                        2"-Amino-2"-deoxydibekacin (Compound IIa)                                                              >100    mg/kg                                        2"-Amino-5,2"-dideoxydibekacin (Compound                                                               50-100  mg/kg                                        IIb)                                                                          ______________________________________                                    

Based on the above elucidation of the biological properties of the newcompounds of general formula (I) and (II) according to this invention,it has been proved that these new compounds not only inhibit stronglythe growth of methicillin-resistant Staphylococcus aureus, but also havebroad and highly effective antibacterial activities againstgram-positive and gram-negative bacteria, including Pseudomonasaeruginosa and are of low toxicity to mammals.

The compounds of general formula (I) and the compounds of generalformula (II) or acid addition salts thereof according to this inventionmay be formulated into various antibacterial compositions containing thesaid compound(s) as active ingredient by blending the same withpharmaceutically acceptable liquid or solid carrier(s) which may be usedconventionally. Anti-bacterial compositions containing the compounds ofgeneral formula (I) or (II) or their acid addition salts of thisinvention may be used primarily in various formulations foradministration, including injections such as intravenous injections,oral compositions such as capsules, tablets, powder and granules, andothers such as ointment, intrarectal agent, suppositories of oil-fattype, water-soluble suppositories, and the like. These variousformulations may be prepared in any conventional manner usingconventional excipients, fillers, binders, wetting agents,disintegrators, surfactants, lubricants, dispersants, buffers,preservatives, dissolution aids, antiseptics, flavorings, indolentagents, and the like.

Generally speaking, 2"-amino-2"-deoxyarbekacin and2"-amino-5,2"-dideoxyarbekacin as represented by general formula (I)according to the first aspect of this invention, as well as2"-amino-2"-deoxydibekacin and 2"-amino-5,2"-dideoxydibekacin asrepresented by general formula (II) according to the second aspect ofthis invention may be prepared by converting the 2"-hydroxyl group ofdibekacin into amino group, and if necessary, acylating the 1-aminogroup of the resulting aminated product with(s)-4-amino-2-hydroxybutyric acid, followed by replacing the 5-hydroxylgroup by a hydrogen atom.

As a process for producing 2"-amino-2"-deoxyarbekacin of formula (Ia)according to the first aspect of this invention, there is provided, in athird aspect of this invention, a process for the preparation of2"-amino-2"-deoxyarbekacin of the following formula (Ia) ##STR8## whichcomprises the steps of: protecting each of the 1- and 3"-amino groups of3,2',6'-N-tris(alkoxycarbonyl)-dibekacin represented by general formula(III) ##STR9## wherein A means an alkoxycarbonyl group serving as anamino-protecting group removable by hydrolysis, with anaralkyioxycarbonyl group which is an amino-protecting group removable byhydrogenolysis, to form a1,3"-N-bis(aralkyl-oxycarbonyl)-3,2',6'-N-tris(alkoxycarbonyl)-dibekacinrepresented by general formula (IV) ##STR10## wherein A has the meaningas defined above and B means an aralkyloxycarbonyl group;

protecting both of the two hydroxyl groups at the 4"-and 6"-positions ofthe compound of general formula (IV) with an aralkylidene or alkylidenegroup as a hydroxyl-protecting group, to form a 4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'-N-tris-(alkoxycarbonyl)-dibekacinrepresented by the following formula (V) ##STR11## wherein A and B havethe meanings as defined above and Y means an aralkylidene or alkylidenegroup;

oxidizing the 2"-hydroxyl group of the compound of formula (V) with anoxidizing agent to form a 4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'-N-tris(alkoxycarbonyl)-2"-deoxy-2"-oxodibekacin represented by the followingformula (VI) ##STR12## wherein A, B and Y have the meanings as definedabove; converting the 2"-oxo group of the compound of formula (VI) into2"-amino group by reducing the same with a hydride in the presence ofammonium acetate, thereby to form a 2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'-N-tris(alkoxycarbonyl)-2"-deoxydibekacinrepresented by the following formula (VII) ##STR13## wherein A, B and Yhave the meanings as defined above; protecting the 2"-amino group of thecompound of formula (VII) with an alkoxycarbonyl group (A) to form a2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis-(aralkyloxycarbonyl)-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacinrepresented by the following formula (VIII) ##STR14## wherein A, B and Yhave the meanings as defined above; eliminating the aralkyloxycarbonylgroups (B) from the 1- and 3"-amino groups by hydrogenolysis to form a2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-depxydibekacinrepresented by the following formula (IX) ##STR15## wherein A and Y havethe meanings as defined above; acylating the 1-amino group of thecompound of formula (IX) with an active ester or acid halide of(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonyl-amino)-2-hydroxybutyric acid represented by the followingformula (X) ##STR16## wherein A' means ap-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group as anamino-protecting group removable by hydrolysis, to form a1-N-[(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonyl-amino)-2-hydroxybutyryl]-2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacinrepresented by the following formula (XI) ##STR17## wherein A, Y and A"have the meanings as defined above; and

hydrolyzing the compound of formula (XI) to remove therefrom thealkoxycarbonyl group (A), the p-alkoxy-substituted-benzyloxycarbonyl oralkoxycarbonyl group (A'), and the aralkylidene or alkylidene group (Y)and to produce the compound of formula (Ia)

3,2',6'-N-Tris(alkoxycarbonyl)-dibekacin of formula (III) to be used asthe starting material in the process of the third aspect of thisinvention may be prepared by reacting dibekacin with an alkoxycarbonylchloride or an active ester equivalant thereto in a suitable organicsolvent such as tetrahydrofuran or dimethylsulfoxide in the presence ofzinc cation in accordance with the process described in thespecification of Japanese Patent Publication Sho-63-1319 or U.S. Pat.No. 4,297,485.

With respect to the process steps for the introduction of analkoxycarbonyl group into each of the 1- and 3"-amino groups of thecompound of formula (III), the introduction of an aralkyliden oralkylidene group into both of the 4"- and 6"-hydroxyl groups of thecompound of formula (IV), the introduction of an alkoxycarbonyl groupinto the 2"-amino group of the compound of formula (VII), thedeprotection of the protected 1- and 3"-amino groups of the compound offormula (VIII), and the deprotection of the 1-N-acylated compound offormula (XI), there may be used known techniques established andconventionally utilizable in the sugar chemistry for the purposes of theprotection of amino group, protection of hydroxyl group, removal ofamino-protecting group and removal of hydroxy-protecting group in ausual manner.

The oxidation of the 2"-hydroxyl group of the compound of formula (V)into oxo group may be carried out by Pfitzner-Moffatt's oxidationmethod, as illustrated hereinafter in relation to "Synthetic ProcessChart A". Then, the conversion of the 2"-oxo group of the compound offormula (VI) into amino group may be effected by such known method forreduction with a hydride in the presence of ammonium acetate, asillustrated in "Synthetic Process Chart A".

Further, the step of acylating the 1-amino group of the compound offormula (IX) with an active ester or an acid halide of anN-protected-(S)-4-amino-2-hydroxybutyric acid of formula (X) may becarried out in accordance with the method for 1-N-acylation ofkanamycins as described in the specifications of Japanese PatentPublication Sho-52-33629, U.S. Pat. No. 4,001,208 and U.S. Pat. No.4,297,485.

Furthermore, as a process for producing 2"-amino-5,2"-dideoxyarbekacinof formula (Ib) according to the first aspect of this invention, thereis provided, in a fourth aspect of this invention, a process for thepreparation of 2"-amino-5,2"-dideoxyarbekacin of the following formula(Ib) ##STR18## which comprises the steps of: eliminating by a knowndeoxygenation method the 5-hydroxyl group of a2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacinrepresented by general formula (VIII) ##STR19## wherein A means analkoxycarbonyl group, B means an aralkyloxycarbonyl group and Y means anaralkylidene or alkylidene group, to form a2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacin represented by the followingformula (XII) ##STR20## wherein A, B and Y have the meanings as definedabove; eliminating the aralkyloxycarbonyl groups (B) from the 1- and3"-amino groups of the compound of formula (XII) to form a2"-amino-4",6"-O-aralkylidene or alkylidene-3,2', 6'2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacin represented by the followingformula (XIII) ##STR21## wherein A and Y have the meanings as definedabove; acylating the 1-amino group of the compound of formula (XIII)with an active ester or acid halide of(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonyl-amino)-2-hydroxybutyric acid represented by the followingformula (X): ##STR22## wherein A' means ap-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group as anamino-protecting group removable by hydrolysis, to form a1-N-[(S)-4-(p-alkoxy-substituted-benzytoxycarbonyl- or oralkoxycarbonyl-amino)-2-hydroxybutyryl]-2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacinrepresented by the following formula (XIV) ##STR23## wherein A, Y and A'have the meanings as defined above; and hydrolyzing the compound offormula (XIV) to remove therefrom the alkoxycarbonyl group (A), thep-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group (A'), andthe aralkylidene or alkylidene group (Y) and to produce the compound offormula (Ib).

In the process of the fourth aspect of this invention, the deoxygenationmethod for effecting the elimination of the 5-hydroxyl group of thecompound of formula (VIII) may conveniently be carried out by atwo-stage process Where the 5-hydroxyl group is first converted intodithiocarbonate group, followed by reducing the latter with a hydride asillustrated hereinafter in relation to "Synthetic Process Chart B".However, any other known deoxygenation method may be adopted, ifdesired.

The step for deprotection of the protected 1- and 3"-amino groups of thecompound of formula (XII) and the step for deprotection of the1-N-acylated product of formula (XIV) may be carried out in a usualmanner similarly to the corresponding step in the process of the thirdaspect of this invention.

Further, the step of acylating the 1- amino group of the compound offormula (XIII) with the butyric acid derivative Of formula (X) may beeffected in a similar manner to that of the corresponding step in theprocess of the third aspect of this invention.

For production of 2"-amino-2"-deoxydibekacin of formula (IIa) accordingto the second aspect of this invention, there is provided, in a fifthaspect of this invention, a process for the preparation of2"-amino-2"-deoxydibekacin of formula (IIa) ##STR24## which comprisesremoving the aralkylidene or alkylidene group (Y) and alkoxycarbonylgroup (A) of a 2"-amino-4", 6"-O-aralkylidene- oralkylidene-3,2',6',2"-N-tetrakis-(alkoxycarbonyl)-2"-deoxydibekacinrepresented by general formula (IX ): ##STR25## wherein A means analkoxycarbonyl group and Y means an aralkylidene or alkylidene group,from the compound of formula (IX) to produce the compound of formula(IIa). Said 2"-amino-4",6"-O-aralkylidene- or alkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacin of formula (IX) mayhave been synthesized via a series of compounds of general formulae(III), (IV), (V), (VI), (VII), and (VIII) mentioned hereinbefore.

Furthermore, for production of 2"-amino-5,2"-dideoxydibekacin of formula(lib) according to the second aspect of this invention, there isprovided, in a sixth aspect of this invention, a process for thepreparation of 2"-amino-5,2"-dideoxydibekacin of formula (IIb) ##STR26##which comprises removing the aralkylidene or alkylidene group (Y) andalkoxycarbonyl group (A) of a 2"-amino-4", 6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacinrepresented by general formula (XIII): ##STR27## wherein A means analkoxycarbonyl group and Y means an aralkylidene or alkylidene group,from the compound of formula (XIII) to produce the compound of formula(IIb). Said 2"-amino 4"-,6"-O-aralkylidene or alkylidene-3,2',6',2"-N-tetrakis (alkoxycarbonyl)-5,2"-dideoxydibekacin of formula(XIII) may have been prepared via the compounds of general formulae(VIII) and (XII) as mentioned hereinbefore.

2"-Amino-2"-deoxydibekacin of formula (IIa) according to the secondaspect of this invention is prepared as set forth in the fifth aspect ofthis invention hereinafter given. It is apparent that the process of thefifth aspect of this invention may also be applied to such cases whenthere is employed the compound of formula (IX) which has been preparedfrom the compounds of general formulae (IV), (V), (VI), (VII) and (VIII)where the amino-protecting groups A and B are.equal to each other.Besides, the process of the sixth aspect of this invention for theproduction of 2"-amino-5,2"-dideoxydibekacin of formula (IIb) may alsobe applied to such cases when there is employed the compound of generalformula (XIII) which has been prepared from the compounds of generalformulae (VIII) and (XII) where the amino-protecting groups A and B areequal to each other. As a known compound examples of the compound ofgeneral formula (IV) which is available as the starting material in theabove cases and in which the amino-protecting groups A and B are thesame, there may be employed1,3,2',6',3"-N-pentakis(t-butyoxycarbonyl)dibekacin [see T. Miyasaka etal., "J. Antibiotics", 33, 527, (1980)].

Now, in respect of the process of the third aspect of this invention,there is given below "Synthetic Process Chart A" which briefly shows apreferred embodiment for carrying out the respective steps of theprocess of the third aspect of this invention, where2"-amino-2"-deoxyarbekacin of formula (Ia) is synthesized starting from3,2',6'-N-tris(t-butoxycarbonyl)dibekacin (Compound IIIa) which is apreferred example of compounds of general formula (III). In "SyntheticProcess Chart A", Boc represents t-butoxycarbonyl group, Z representsbenzyloxycarbonyl group, Ph denotes phenyl group, and PMZ denotesp-methoxybenzyloxycarbonyl group (the same applies to the other Chartsgiven hereinafter).

Synthetic Process Chart A ##STR28##

"Synthetic Process Chart B" given below briefly shows an embodiment forcarrying out the respective steps of the process of the fourth aspect ofthis invention, where 2"-amino-5,2"-dideoxyarbekacin of formula (Ib) issynthesized using the compound of formula (VIIIa) which is obtained asan intermediate in "Synthetic Process Chart A" above which shows apreferred embodiment of the process of the third aspect of thisinvention.

Synthetic Process Chart B ##STR29##

"Synthetic Process Chart C" given below briefly shows a step of theprocess according to the fifth aspect of this invention, where2"-amino-2"-deoxydibekacin of formula (IIa) is synthesized using thecompound of formula (IXa) which is obtained as an intermediate in"Synthetic Process Chart A" which shows a preferred embodiment forcarrying out the process of the third aspect of this invention.

Synthetic Process Chart C ##STR30##

"Synthetic Process Chart D" given below briefly shows a step of theprocess according to the sixth aspect of this invention, where2"-amino-5,2"-dideoxydibekacin of formula (IIb) is synthesized using thecompound of formula (XIIIa) which is obtained as an intermediate in"Synthetic Process Chart B" above which shows a preferred embodiment orcarrying out the process of the third aspect of this invention.

Synthetic Process Chart D ##STR31##

The following is some detailed descriptions about Synthetic ProcessChart A above which illustrates a preferred embodiment for carrying outthe process for the preparation of the compound of formula (Ia) i.e.2"-amino-2"-deoxyarbekacin according to the third aspect of thisinvention.

3,2',6'-N-Tris(t-butoxycarbonyl)-dibekacin of formula (IIIa)(hereinafter simply referred to as 3,2',6'-N-tris(BOC)dibekacin) whichis to be used as the starting material is a partially amino-protectedderivative of dibekacin which may be synthesized by acylating dibekacinwith t-butoxycarbonyl chloride in the presence Of zinc acetate asdescribed in the specification of Japanese Patent PublicationSho-63-1319 or U.S. Pat. No. 4,297,485.

As depicted in Synthetic Process Chart A, the compound of formula (IVa),i.e.1,3"-N-bis(benzyloxy-carbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-dibekacinis produced by protecting in a usual manner each of the two amino groupsat the 1- and 3"-positions of 3,2',6'-N-tris(BOC)dibekacin (IIIa) withan amino-protecting group which is removable by a deprotecting methoddifferent from that for the removal of BOC, and which is, for example,benzyloxycarbonyl group, one of aralkyloxycarbonyl groups. Subsequently,the two hydroxyl groups at the 4"- and 6"-positions of the compound(IVa) are protected simultaneously with a benzylidene group which is oneof aralkylidene groups, whereby to form the compound of formula (Va),i.e.4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-dibekacin.

The 2"-OH group of the compound (Va) is then converted into amino group.The conversion of the 2"-OH group into amino group may be achieved, forexample, by a usual method of Pfitzner-Moffatt for oxidation [B. P.Mundy and M. G. Ellerd, "Name Reactions and Reagents in OrganicSynthesis", John Wiley & Sons, New York, p.162 (1988)], thus forming the2"-keto derivatives of formula (VIa), i.e.4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-2"-deoxy-2"-oxodibekacin,followed by subjecting the compound (VIa) to a reductive amination knownper se [for example, R. F. Borch et al., "J. Am. Chem. Soc." 93, 2897(1971)] for the conversion of the 2"-oxo group into 2"-amino group. Wehave found that equatorial 2"-NH₂ group is preferentially formed byadopting this reductive amination. The said reductive amination reactionmay be effected by reduction of the compound (VIa) with a hydride, forexample, sodium cyanoborohydride in the presence of ammonium acetate.

Thus, there is produced the 2"-amino derivative of formula (VIIa), i.e.2"-amino-4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-2"-deoxydibekacin.

Then, the 2"-amino group of the compound of formula (VIIa) is protectedwith BOC group as amino-protecting group to afford the compound offormula (VIIIa), i.e.2"-amino-4",6"-O-benzylide-1,3"-N-bis(benzyloxycarbony)-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-2"-deoxydibekacin.Subsequently, the 1- and 3"-benzyloxycarbonyl groups of the compound(VIIIa) are removed by hydrogenolysis in a usual manner to give thecompound of formula (IXa), i.e.2"-amino-4",6"-O-benzylidene-3,2'6',2"-N-tetrakis(t-butoxycarbonyl)-2"-deoxydibekacin. The 1- amino group of the compound(IXa) is then acylated preferentially with (S)-4-amino-2-hydroxybutyricacid whose amino group has been protected withp-methoxybenzyloxycarbonyl group, by a known 1-N-acylating method.Subsequently, the resulting 1-N-acylated product of formula (XIa) istreated with aqueous trifluoroacetic acid or the like to remove theamino-protecting groups and the hydroxy-protecting groups all at once.The product thus obtained is purified by a column chromatography using aweak cation-exchange resin to yield 2"-amino-2"-deoxyarbekacin offormula (Ia) which has only one acylated-amino group at the 1-positionas the object product.

Each of the reaction steps of Synthetic Process Chart A will beillustrated in more detail in Example 1 given later.

Some further explanation is now given on Synthetic Process Chart B.5-Deoxy derivative of formula (XIIa), i.e.2"-amino-2",6"-O-benzylidene-1,3-N-bis(benzyloxycarbonyl)-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-5,2"-dideoxydibekacin is prepared by converting the5-OH group of the compound of formula (VIIIa) shown in the aboveSynthetic Process Chart A into a dithiocarbonate group (H₃ CSC(═S)O--)and reducing said group with a hydride according to a knowndeoxygenation method [e.g. T. Hayashi et al., "Chem. Pharm. Bull.", 26,1786, (1978)].

The 1-N-acylated product of formula (XIVa) is prepared by removing thebenzyloxycarbonyl group from each of the protected 1- and 3"-aminogroups of the compound of formula (XIIa) in the same manner as for thecompound of formula (VIIIa) shown in Synthetic Process Chart A, toafford the compound of formula (XIIIa), i.e.2"-amino-4",6"-O-benzylidene-3,2', 6',2"-N-tetrakis(t-butoxycarbonyl)-5,2"-dideoxydibekacin, followed by acylating the1-amino group with (S)-4-amino-2-hydroxybutyric acid whose amino grouphas been protected by p-methoxybenzyloxycarbonyl group. The compound offormula (XIVa) thus obtained is then deprotected by hydrolysis withaqueous trifluoroacetic acid or another suitable acid to remove thebenzylidene group and amino-protecting groups, thus affording the objectcompound, 2"-amino-5,2"-dideoxyarbekacin of formula (Ib).

Each of the reaction steps of Synthetic Process Chart B will beillustrated in more detail in Example 2 given below.

An explanation is now given on Synthetic Process Chart C. Thus, when thecompound of formula (IXa) shown in Synthetic Process Chart A issubjected to conventional deprotecting reactions,2"-amino-2"-deoxydibekacin of formula (IIa) is produced (see Example 3given later).

Further, an explanation is given on Synthetic Process Chart D. Thus,when the compound of formula (XIIIa) shown in Synthetic Process Chart Bis subjected to conventional deprotecting reactions,2"-amino-5,2"-dideoxydibekacin of formula (IIb) is produced (see Example4 given later).

As described in this specification hereinbefore,2"-amino-2"-deoxydibekacin, 2"-amino-2"-deoxyarbekacin and their 5-deoxyderivatives which are hardly susceptible of the enzymaticphosphorylation at their 2"-position have now been provided according tothis invention as the new antibiotics which are active againstmethicillin-resistant Staphylococcus aureus (MRSA). On the other hand,we, the present inventors, have been aware of that as a modified5-hydroxyl derivative of sisomicin which is one of the aminoglycosidicantibiotics containing deoxystreptamine moiety, there are known5-epi-amino-5-deoxysisomicin and 5-epi-fluoro-5-deoxysisomicinrepresented by general formula (B) ##STR32## wherein R means an aminogroup for 5-epi-amino-5-deoxysisomicin or R means a fluorine atom for5-epi-fluoro-5-deoxysisomicin, and that these 5-epi derivatives ofsisomicin have good antibacterial activity (see P. J. L. Daniels et al"Aminoglycoside Antibiotics" edited by K. L. Reinhart, Jr. and T. Suami,pages 371-392 (1980), American Chemical Society, Washington).

We have recently found that 2"-amino-5,2"-dideoxyarbekacin provided inthe first aspect of this invention can exhibit broad and excellentantibacterial activity against a variety of gram-positive andgram-negative bacteria, including MRSA, but shows a higher acutetoxicity to mice than that of 2"-amino-2"-deoxyarbekacin. Accordingly,we have made further studies in an attempt to provide another newarbekacin derivatives which are of reduced acute toxicity but showexcellent antibacterial activity.

Thus, we have now studied chemical synthesis of5-substituted-2"-amino-2"-deoxyarbekacins and succeeded in synthesizing2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin and2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin represented by generalformula (XVI) shown below. Moreover, it has been found that these newtwo derivatives of arbekacin having general formula (XVI) can stronglyinhibit the growth of MRSA and further exhibit broad and effectiveantibacterial activity against a variety of gram-positive andgram-negative bacteria but have reduced toxicity to mammals.

According to a seventh aspect of this invention, therefore, there areprovided a 5-substituted-2"-amino-2"-deoxyarbekacin represented by thefollowing general formula (XVI) ##STR33## wherein R¹ means a fluorineatom or an amino group, and an acid addition salt thereof.

The compound of general formula (XVI) where R¹ means a fluorine atom is2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin represented by the followingformula (XVIa) ##STR34##

The compound of general formula (XVI) where R¹ means an amino group is2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin represented by the followingformula (XVIb) ##STR35##

Physico-chemical properties of the new compounds provided according tothe seventh aspect of this invention, namely2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin of formula (XVIa) and2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin of formula (XVIb) aredescribed below:

[1] 2"-Amino-5,2"-dideoxy-5-epi-fluoroarbekacin [Compound XVIa]

(1) Color and form: colorless powder

(2) Molecular formula: C₂₂ H₄₄ FN₇ O₈

(3) Mass spectrum (SI-MS): m/z 554(M+H)⁺

(4) Melting point: 164°-171° C. (decomposed)

(5) Optical rotation [α]_(D) ²⁰ +108° (c 1.0, H₂ O)

(6) UV and visible ray-absorption spectra: no specific absorption

(7) Infrared absorption spectrum (KBr): 3400, 1660 1600, 1490, 1400,1350, 1130, 1060, 860 cm⁻¹

(8) ¹ H-NMR spectrum(D₂ O, pD 2): δ1.66(1H, m, 4'ax-H), 1.85-1.99 (3H,m, 2ax-H, 4'eq-H, 3"-H), 2.00-2.11(2H, m, 3'-H₂), 2.22(1H, m, 3'"-H),2.41(1H, m, 2eq-H), 3.11(1H, dd, J=7.7, 11.3 Hz, 6'-H), 3.19 (1H, t,4'"-H), 3.28 (1H, dd, 6'-H), 3.61 (1H, m, 2'-H), 3.70 (1H, dd, J=9.7,10.0 Hz, 4"-H) 3.77(1H, dd, J-12.3 Hz, 6"-H), 3.79 (1H, t, J=11.3 Hz,3"-H), 3.85 (1H, m, 3-H), 3.90 (1H, dd, J=3.9 Hz, 2"-H), 4.01 (1H, d,6"-H), 4.07(1H, m, 5"-H), 4.12(1H, m, 5'-H), 4.29(1H, dd, J=10.8, 25.9Hz, 4-H), 4.30-4.34 (2H, m, 1-H, 6-H), 4.35(1H, dd, J=4.0, 9.4 Hz,2'"-H), 5.49(1H, d, J=3,4 Hz, 1'-H), 5.53(1H, d, J=3.9 Hz, 1"-H), 5.72(1H, d, J=51.0 Hz, 5-H)

(9) Solubility: easily soluble in water

(10) Distinction between basic, acidic and neutral substances in nature:basic substance

[2] 2-Amino-5,2"-dideoxy-5-epi-aminoarbekacin [Compound XVIb ]

(1) Color and form: colorless powder

(2) Molecular formula: C₂₂ H₄₆ N₈ O₈

(3) Mass spectrum(FD-MS): m/z 551(M+H)⁺

(4) Melting point: 192°-199° C. (decomposed)

(5) Optical rotation: [α]_(D) ²⁰ +102° (c 1.0, H₂ O)

(6) UV and visible ray-absorption spectra: no specific absorption

(7) Infrared absorption spectrum (KBr): 3420, 1650, 1590, 1480, 1400,1350, 1120, 1040, 830 cm⁻¹

(8) ¹ H-NMR spectrum(D₂ O, pD 2): δ1.71(1H, m, 4'-ax-H), 1.92-2.07 (3H,m, 2ax-H, 4'eq-H, 3'"-H), 2.10-2.15 (2H, m, 3'-H₂), 2.21 (1H, m, 3'"-H),2.45(1H, dt, J=4.7, 13.3 Hz, 2eq-H), 3.19(1H, t, J=6.9 Hz, 4'"-H),3.22(1H, dd, J=6.4 Hz, 6'-H), 3.34(1H, dd, J=3.6 Hz, 6'-H), 3.74(1H, m,2'-H), 3.78-3.88(4H, m, 3-H, 3"-H, 4"-H, 6"-H), 3.93-3.95(2H, m, 4-H2"-H), 4.03(1H, d, J=11, 1 Hz, 6"-H), 4.17(1H, ddd, 5'-H), 4.37(1H, dd,J=3.6, 9.4 Hz, 2'"-H), 4.46(1H, td, 1-H), 4.57(1H, br, 5-H), 4.59(1H, m,5"-H), 4.68(1H, dd, J=3.3, 11.1 Hz, 6-H), 5.54(1H, d, J=3.3 Hz, 1-H),5.58(1H, d, J=2.2 Hz, 1"-H)

(9) Solubility: easily soluble in water

(10) Distinction between basic, acidic and neutral substances in nature:basic substance

Similarly to the new arbekacin derivatives of general formula (I)according to the first aspect of this invention,2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin of formula (XVIa) and2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin of formula (XVIb) accordingto the seventh aspect of this invention can form their acid additionsalts which include such those with a pharmaceutically acceptableinorganic acid, e.g. hydrochloric acid, sulfuric acid, phosphoric acid,nitric acid and the like or with a pharmaceutically acceptable organicacid, e.g. malic acid, citric acid, ascorbic acid, methanesulfonic acidand the like.

Biological properties of the new5-substituted-2"-amino-2"-deoxyarbekacins provided according to theseventh aspect of this invention are next described.

(1) Antibacterial activities

Minimum growth inhibitory concentrations (MIC) of each of2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin (Compound XVIa) and2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin (Compound XVIb) againstvarious bacteria (18 strains) and against clinically isolated strains ofMRSA (50 strains) were determined by standard serial dilution method onMuller-Hinton's agar medium (as estimated after cultivation at 27° C.for 18 hours), and the test results obtained are shown in TABLE 5 andTABLE 6, respectively.

                  TABLE 5                                                         ______________________________________                                                         MIC. (wg/mt)                                                                    Compound   Compound                                        Test organisms     XVIa       XVIb                                            ______________________________________                                        Staphylococcus aureus FDA209P                                                                    0.78       ≦0.20                                    S. aureus Smith    ≦0.20                                                                             ≦0.20                                    S. epidermidis 109 0.78       0.39                                            Bacillus subtilis PCI219                                                                         0.39       ≦0.20                                    Escherichia coli NIHJ                                                                            0.78       0.78                                            E. coli K-12 MLI629                                                                              3.13       1.56                                            E. coli K-12 LA290 R55                                                                           1.56       1.56                                            E. coli JR66/W677  3.13       3.13                                            Klebsiella pneumoniae PCI602                                                                     1.56       1.56                                            Shigella dysenteriae JSI1910                                                                     3.13       3.13                                            Salmonella typhi T-63                                                                            0.78       0.78                                            Proteus vulgaris OX19                                                                            1.56       1.56                                            Providencia rettgeri GN311                                                                       1.56       1.56                                            Serratia marcescens                                                                              1.56       3.13                                            Pseudomonas aeruginosa A3                                                                        0.78       0.39                                            P. aeruginosa H9   3.13       3.13                                            P. aeruginosa TI-13                                                                              1.56       1.56                                            P. aeruginosa PST1 12.5       6.25                                            ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                                   Antibacterial MIC spectra                                                     (μg/ml) against 50 clinically                                   Test compound                                                                            isolated strains of MRSA                                                                        MIC.sub.50                                                                            MIC.sub.90                               ______________________________________                                        Compound XVIa                                                                            0.39-3.13         0.78    1.56                                     Compound XVIB                                                                            0.39-1.56         0.78    1.56                                     DKB        ≦0.20->100 50      >100                                     (comparative)                                                                 ABK        ≦0.20-6.25 0.39    6.25                                     (comparative)                                                                 ______________________________________                                         Note:- MIC.sub.50 or MIC.sub.90 represents the concentration of tested        active compound at which 50% or 90% of the total numbers of the bacterial     strains tested were inhibited from their growth. DKB denotes dibekacin,       and ABK denotes arbekacin.                                               

(2) Acute toxicity

50% Lethal dosages (LD₅₀, observations for two weeks) of the newcompounds of general formula (XVI) according to the seventh aspect ofthis invention as estimated upon single intravenous administration tomice (ICR-strain, 4 weeks old, female) are as follows:

    ______________________________________                                                               LD.sub.50                                              ______________________________________                                        2"-Amino-5,2"-dideoxy-5-epi-fluoroarbekacin                                                            >100 mg/kg                                           (Compound XVIa)                                                               2"-Amino-5,2"-dideoxy-5-epi-aminoarbekacin                                                             >100 mg/kg                                           (Compound XVIb)                                                               ______________________________________                                    

Based on the above elucidation of the biological properties of the newcompounds of formulae (XVIa) and (XVIb) according to the seventh aspectof this invention, it has been proved that these new compounds ofgeneral formula (XVI) again not only inhibit strongly the growth ofmethicillin-resistant Staphylococcus aureus, but also have broad andhighly effective antibacterial activities against gram-positive andgram-negative bacteria, including Pseudomonas aeruginosa and are ofreduced toxicity to mammals.

The compound of formula (XVIa) and the compound of formula (XVIb) oracid addition salts thereof according to the seventh aspect of thisinvention may be formulated into various antibacterial compositionscontaining the said compound(s) as active ingredient by blending thesame with pharmaceutically acceptable liquid or solid carrier(s) whichmay be used conventionally. Antibacterial compositions containing thecompound of formulae (XVIa) or (XVIb) or their acid addition salt may beused primarily in various formulations for administration, includinginjections such as intravenous injections, oral compositions such ascapsules, tablets, powder and granules, and others such as ointment,intrarectal agent, suppositories of oil-fat type, water-solublesuppositories, and the like. These various formulations may be preparedin any conventional manner with using conventional excipients, fillers,binders, wetting agents, disintegrators, surfactants, lubricants,dispersants, buffers, preservatives, dissolution aids, antiseptics,flavorings, indolent agents, and the like.

The 5-substituted-2"-amino-2"-deoxyarbekacins of general formula (XVI)according to the seventh aspect of this invention can be produced withusing as a starting compound the new compound,2"-amino-2"-deoxyarbekacin of formula (Ia) obtained in the first aspectof this invention described hereinbefore.

For the production of 2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin offormula (XVIa) according to the seventh aspect of this invention, thereis provided in an eighth aspect of this invention a process for thepreparation of 2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin of thefollowing formula (XVIa) ##STR36## which comprises the steps of:protecting all the six amino groups of 2"-amino-2"-deoxyarbekacin offormula (XVII) ##STR37## with an alkoxycarbonyl group which serves as anamino-protecting group readily removable by hydrolysis, followed byprotecting the 4"-, 6"- and 2'"-hydroxyl groups of the resultingN-alkoxycarbonylated 2"-amino-2"-deoxyarbekacin through selectiveacylation of these hydroxyl groups with an alkanoyl group, thereby toproduce from said 2"-amino-2"-deocyarbekacin, a4",6",2"-tri-O-acyl-3,2',6',2",3",4'"-N-hexakis(alkoxycarbonyl)-2"-amino-2"-deoxyarbekacinrepresented by general formula (XVIIa) ##STR38## wherein A means analkoxycarbonyl group as the amino-protecting group removable byhydrolysis and B¹ means a lower alkanoyl group as thehydroxyl-protecting group removable by hydrolysis;

then reacting a fluorination agent with the compound of formula (XVIIa)to introduce a fluorine atom in the axial direction into the 5-positionof the same compound (XVIIa) and thereby to produce a 5-epi-fluoroderivative represented by the following general formula (XVIIIa)##STR39## wherein A means the amino-protecting group as defined aboveand B¹ means the hydroxyl-protecting group as defined above; and

effecting the removal of the amino-protecting groups by acidichydrolysis and the removal of the hydroxyl-protecting groups by alkalinehydrolysis from the compound of general formula (XVIIIa) to produce thecompound of formula (XVIa).

Here, it is to be noted that the compound of formula (XVII) shown justabove is identical to the compound of formula (Ia) given hereinbeforefor the first aspect of this invention, that is,2"-amino-2"-deoxyarbekacin.

The amino-protecting group (A) which may be available and introducedinto the amino groups of the starting compound of formula (XVII) in theprocess of the eighth aspect of this invention includes a knownalkoxycarbonyl group such as t-butoxycarbonyl group, as well as anaralkyloxycarbonyl group such as p-methoxybenzyloxycarbonyl group etc.,which are readily removable by acidic hydrolysis. The introduction ofsuch amino-protecting group into amino groups of the compound (XVII) maybe effected by a conventional technique for protection of amino groupsas known in the art of peptide chemistry. The acyl group, particularlyan alkanoyl group (B¹) which may be available and introduced into somehydroxyl groups of the compound (XVII) includes an alkanoyl groupcontaining 2-5 carbon atoms which is easily removable by alkalinehydrolysis. For instance, such a compound of general formula (XVIIa)where A is the amino-protecting group as set out above but B¹ is still ahydrogen atom, for example, a3,2',6',2",3",4'"-N-hexakis(alkoxycarbonyl)-2"-amino-2"-deoxyarbekacinmay be reacted with an acylating agent, e.g. acetyl anhydride inpyridine so that the acyl group, e.g. acetyl group is preferentially andefficiently introduced into each of the three hydroxyl groups at the 4"-6"- and 2'"-positions of the compound employed, whereby there is formedsuch a compound of general formula (XVIIa) where A is theamino-protecting group, B¹ is the hydroxyl-protecting acyl group asintroduced but the 5-hydroxyl group remains unprotected, for example, a4",6",2'"-tri-O-acyl-3,2',6',2",3",4'"-N-hexakis(alkoxycarbonyl)-2"-amino-2"-deoxyarbekacin.

For replacement of the 5-hydroxyl group of the compound of formula(XVIIa) by a fluorine atom, this compound is reacted with a knownfluorination agent, for example, a dialkylsulfur trifluoride such asdimethylsulfur trifluoride or a dialkylaminosulfur trifluoride such asdiethylaminosulfur trifluoride (usually abbreviated as DAST) and thelike. This fluorination reaction can be conducted in dichloromethane inthe presence of pyridine at ambient temperature.

This fluorination reaction gives the compound of general formula(XVIIIa). The latter compound is then subjected to a conventional methodfor removal of the amino-protecting group by acidic hydrolysis to removethe amino-protecting groups (A) therefrom. The resulting N-unprotectedproduct is subsequently subjected to a conventional method for removalof the hydroxyl-protecting groups by alkaline hydrolysis to remove thehydroxyl-protecting protecting groups (B¹) therefrom. There is thusproduced the compound of formula (XVIa) as aimed at in the eighth aspectof this invention.

For the production of 2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin offormula (XVIb) according to the seventh aspect of this invention, thereis provided in a ninth aspect of this invention a process for thepreparation of 2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin of thefollowing formula (XVIb) ##STR40## which comprises the steps of:alkylsulfonylating the 5-hydroxyl group of a 4",6",2'"-tri-O-acyl-3,2',6',2",3",4'"-N-hexakis(alkoxycarbonyl)-2"-amino-2"-deoxyarbekacinrepresented by general formula (XVIIa) ##STR41## wherein A means analkoxycarbonyl group as an amino-protecting group and B¹ means a loweralkanoyl group as a hydroxyl-protecting group, to form a5-O-alkylsulfonylated derivative represented by the following generalformula (XVlIb) ##STR42## wherein A and B¹ have the same meanings asdefined above and E means an alkylsulfonyl group;

then reacting an azidation agent with the alkylsulfonyloxy group at the5-position of the compound of general formula (XVIIb) to introduce anazido group in the axial direction into the 5-position of the samecompound and thereby to produce a 5-epi-azido derivative represented bygeneral formula (XVIIIb) ##STR43## wherein A and B¹ have the samemeanings as defined above; subsequently hydrogenating the compound ofgeneral formula (XVIIIb) to form a 5-epi-amino derivative represented bythe following general formula (XVIIIc) ##STR44## wherein A and B havethe same meanings as defined above, and effecting the removal of theamino-protecting groups by acidic hydrolysis and the removal of thehydroxyl-protecting groups by alkaline hydrolysis from the compound ofgeneral formula (XVIIIc) to produce the compound of formula (XVIb).

In respect of the process according to the ninth aspect of thisinvention, the amino-protecting group (A) available in the startingcompound of general formula (XVIIa) may include a known alkoxycarbonylgroup such as t-butoxycarbonyl group and an aralkyloxycarbonyl groupsuch as p-methoxybenzyloxycarbonyl group which are readily removable byacidic hydrolysis. The hydroxyl-protecting acyl group (B¹) available inthe same compound (XVIIa) may include a C₂ -C₅ alkanoyl group which isreadily removable by alkaline hydrolysis. These protective groups (A andB¹) present in the compound (XVIIa) may respectively be the same as theamino-protecting group (A) and the hydroxyl-protecting group (B) presentin the compound of general formula (XVIIa) as employed in the process ofthe eighth aspect of this invention.

In the process of the ninth aspect of this invention, the compound ofgeneral formula (XVIIa) is used and the 5-hydroxyl group of thiscompound is first alkylsulfonylated, for example, methanesulfonylated(i.e. mesylated) in a known manner to give a 5-O-alkylsulfonylatedderivative of general formula (XVIIb). This derivative (XVIIb) is thenreacted with a known azidation reagent such as sodium azide to effect anucleophilic substitution reaction for replacing the 5-alkylsulfonyloxygroup by azido group with accompanying inversion of the configuration ofthe 5-substituent, whereby there is formed the 5-epi-azido derivative ofgeneral formula (XVIIIb). Subsequently, in order to convert the 5-azidogroup into amino group, the compound of general formula (XVIIIb) issubjected to a catalytic reduction in a known manner using Ranney nickelas catalyst. In this way, the 5-epi-amino derivative of general formula(XVIIIc) is produced.

The 5-epi-amino derivative of general formula (XVIIIc) as produced fromthe above step of catalytic reduction is then subjected to aconventional method for removal of the amino-protecting group by acidichydrolysis to remove the amino-protecting groups (A) therefrom. Theresulting N-unprotected product is subsequently subjected to aconventional method for removal of the hydroxyl-protecting group byalkaline hydrolysis to remove the hydroxyl-protecting groups (B¹)therefrom. There is thus produced the compound of formula (XVIb) asaimed at in the ninth aspect of this invention.

Furthermore, an antibacterial composition which contains a new compoundof this invention having the formula (Ia), (Ib), (IIa), (IIb), (XVIa) or(XVIb) given hereinbefore or an acid addition salt thereof as the activeingredient may be prepared by mixing the active compound with one ormore known liquid or solid carrier(s) of various kinds in appropriateproportions, and optionally further incorporating one or more knownadditives into the composition. The dosage of the new compound of thisinvention when administered will depend on the nature of diseases to betreated, conditions of the diseases and other different factors, but itsoptimum dosage can be decided by ordinary and appropriate, preliminarytests.

According to a tenth aspect of this invention, therefore, there isprovided an antibacterial composition comprising2"-amino-2"-deoxyarbekacin, 2"-amino-5,2"-dideoxyarbekacin or an acidaddition salt thereof as active ingredient, in combination with apharmaceutically acceptable carrier for the active ingredient.

According to a further aspect of this invention, there is provided anantibacterial composition comprising 2"-amino-2"-deoxydibekacin,2"-amino-5,2"-dideoxydibekacin or an acid addition salt thereof asactive ingredient, in combination with a pharmaceutically acceptablecarrier for the active ingredient.

According to further another aspect of this invention, there is providedan antibacterial composition comprising2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin,2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin or an acid addition saltthereof as active ingredient, in combination with a pharmaceuticallyacceptable carrier for the active ingredient.

This invention further includes use of 2"-amino-2-deoxyarbekacin,2"-amino-5,2"-dideoxyarbekacin,2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin,2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin, 2"-amino-2"-deoxydibekacin,2"-amino-5,2"-dideoxydibekacin or an acid addition salt thereof in themanufacture of an antibacterial composition.

The first to sixth aspects of this invention are next illustrated withreference to the following Examples 1-4 to which this invention is notlimited.

EXAMPLE 1 Synthesis of 2"-amino-2"-deoxyarbekacin (Compound Ia)

(1)4",6"-O-Benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-dibekacin(Compound Va):

3,2',6'-N-tris(t-butoxycarbonyl)-dibekacin (Compound IIIa) (9.02g; 12.0mmol), which is described in the specification of Japanese PatentPublication Sho-63-1319 or U.S. Pat. No. 4,297,485, was dissolved inN,N-dimethylformamide (DMF) (50 ml). To the resulting solution wereadded pyridine (10 ml) and N-(benzyloxycarbonyl)-succinimide (6.28g) andthe reaction was conducted at room temperature for 4 hours (forbenzyloxycarbonylation of the 1- and 3"-amino groups). The resultingreaction solution was concentrated under a reduced pressure, followed byaddition of water, and the precipitate thus formed was washed with waterand ethyl ether to afford1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-dibekacin(9.90 g) (Compound IVa). FD-MS m/z 1020(M+H)⁺.

The 1,3"-N-bis(benzyloxycarbonyl) derivative obtained (4.98 g) wasdissolved in DMF, and to the solution were added benzaldehydedimethylacetal (3 ml) and anhydrous p-toluenesulfonic acid (200 mg). Theresultant mixture was heated at 40° C. under a reduced pressure of 20 mmHg with stirring for 1 hour to conduct the reaction (for 4",6"-O-benzylidenation). The resulting reaction solution was extractedwith chloroform (300 ml) added and the extract was washed with asaturated aqueous sodium hydrogen carbonate solution (50 ml) and with a10% aqueous sodium chloride solution (50 ml) and then concentrated todryness. The residue was reprecipitated from a hot mixture oftetrahydrofuran (THF) and ethyl acetate, affording the titled compound(3.88 g). [α]_(D) ²⁰ +50° (c 1.2, DMF).

(2)2"-Amino-4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-2"-deoxydibekacin(Compound VIIIa):

The compound (2.95 g) obtained in the above item (1) was dissolved inanhydrous dimethylsulfoxide (DMSO) (13 ml), to which pyridiniumtrifluoroacetate (250 mg) was then added. To the resulting solution, asolution of dicyclohexylcarbodiimide (1.68 g) in benzene (19 ml) wasadded, and the mixture obtained was stirred at room temperatureovernight to conduct the oxidation reaction intended. A solution ofoxalic acid dihydrate (685 mg) in dioxane (2.5 ml) was added dropwise tothe resulting reaction solution, and the mixture obtained was stirred atroom temperature for 30 minutes. The precipitate thus formed wasfiltered off and the filtrate was extracted with chloroform (180 ml)added. The extract was washed with a saturated aqueous sodium hydrogencarbonate solution (100 ml) and a 10% aqueous sodium chloride solution(200 ml) and then concentrated to dryness to afford the 2"-ketoderivative, more specifically4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-2"-deoxy-2"-oxodibekacin (Compound VIa) (3.35 g).

The 2"-keto compound thus prepared was dissolved in anhydrous methanol(100 ml), to which ammonium acetate (3.7 g) and sodium cyanoborohydride(673 mg) were added in order, and the mixture obtained was stirred atroom temperature overnight to effect the reductive amination reaction.The resulting reaction solution was extracted with chloroform (300 ml)added, and the extract was washed with water, a saturated agueous sodiumhydrogen carbonate solution and a 10% aqueous sodium chloride solution(100 ml each), successively, and then concentrated. Thereafter, theconcentrate was purified by passing through a silica gel column (Wakogel C-300, a product of Wako Junyaku Kogyo K.K.; with diameter of 40 mmand height of 70 cm), eluting with chloroform-methanol (40:1), then withchloroform-methanol (20:1), collecting fractions containing the2"-aminated derivative, more specifically 2"-amino-4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6'-N-tris(t-butoxycarbonyl)-2"-deoxydibekacin(Compound VIIa) (which shows a value of Rf=0.16 when developed withchloroform-methanol (20:1) in the silica gel thin layer chromatography),and concentrating the fractions collected to dryness (775 mg).

The residne obtained was dissolved in a mixture of THF-methanol (1:1)(26 ml), to which were then added triethylamine (0.1 ml) and di-t-butyldicarbonate (0.3 ml), and the resulting mixture was allowed to standovernight at room temperature (for t-butoxycarbonylation reaction of the2"-amino group). The resultant reaction solution was concentrated todryness and the residue was purified by chromatography on a silica gelcolumn (with diameter of 22 mm and height of 18 cm) as developed withchloroform-methanol (20:1), to afford the titled compound (752 mg).FD-MS m/z 1207(M+H)⁺, [α]_(D) ²⁰ +33° (c 1, CHCl₃).

(3)2"-Amino-4",6"-O-benzylidene-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-2"-deoxydibekacin(Compound IXa)

The compound (730 mg) obtained in the above item (2) was dissolved in amixture (1:19) of 88% formic acid and methanol (40 ml), to which wasthen added 10% palladium-carbon (1.45 g) in an argon atmosphere, and theresulting admixture was subjected to hydrogenolysis (for 2 hours) toremove the benzyloxycarbonyl group from each of the 1- and 3"-aminogroups. The reaction solution obtained was filtered, followed byconcentrating to dryness to yield the titled compound (491 mg).

(4) 2"-Amino-2"-deoxyarbekacin (Compound Ia)

The compound (246 mg) obtained in the above item (3) was dissolved inTHF (6 ml), to which was added triethylamine (35 μl). To the resultingsolution was added a solution of an active ester which was prepared byadding N-hydroxysuccinimide (33 mg) and dicyclohexylcarbodiimide (61 mg)to (S)-4-(p-methoxybenzyloxycarbonylamino)-2-hydroxybutyric acid (81 mg)in THF (1.4 ml). The reaction mixture was agitated overnight at 5°-20°C. to effect the reaction. The resulting reaction solution was filteredto remove a small amount of insoluble matters and the filtrate wasconcentrated to dryness. The residue obtained was dissolved inchloroform (6 ml) and the solution was washed with a saturated aqueoussodium hydrogen carbonate solution (2 ml), then With a 10% aqueoussodium chloride solution (2 ml) and then concentrated to dryness. Theresidue obtained (269 mg) was purified by chromatography on a silica gelcolumn (with diameter of 22 mm and height of 36 cm) as eluted first withchloroform, and then with a mixture (20:1) of chloroform and methanol,1-N-[(S)-4-(p-methoxybenzyloxycarbonylamino)-2-hydroxybutyryl]-2"-amino-4",6"-O-benzylidene-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-2"-deoxydibekacin(Compound XIa) (139 mg) was obtained as the 1-N-acylated product.

This compound was dissolved in a 90% trifluoroacetic acid (2.8 ml) andthe solution was allowed to stand at room temperature for 1 hour toeffect the removal of the benzylidene group, the removal of thet-butoxycarbonyl group and the removal of the p-methoxybenzyloxycarbonylgroup (for the deprotections). Then, the resulting reaction solution wasconcentrated to dryness and washed with ether (9 ml). The residue waspurified by dissolving in a small amount of water and passing theaqueous solution through a column of Amberlite CG-50 (NH₄ ⁺ form, 25 ml,a product of Rohm & Haas Company, U.S.A.), followed by washing thecolumn with water (40 ml) and by gradiently eluting with 0.1˜1.5Maqueous ammonia solutions. Thus, the object product,2"-amino-2"-deoxyarbekacin (38 mg) was yielded.

EXAMPLE 2 Synthesis of 2"-amino-5,2"-dideoxyarbekacin (Compound Ib)

(1)2"-Amino-4",6"-O-benzylidene-1,3"-N-bis(benzyloxycarbonyl)-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-5,2"-dideoxydibekacin(Compound XIIa):

The compound (VIIIa) (184 mg) obtained in EXAMPLE 1 (2) above wasdissolved in DMSO (1.6 ml), to which was then added carbon disulfide(0.8 ml). To the resulting mixture under vigorously stirring, an aqueous8M NaOH (0.6 ml) was added dropwise, and after continuing the stirringat room temperature for 30 minutes, methyl iodide (1.6 ml) was addedthereto. The resulting reaction mixture was further stirred for 2 hours.The reaction solution obtained was then concentrated to dryness and theresidue was dissolved in chloroform (15 ml) and the resulting solutionwas washed with water (15 ml) and then concentrated to dryness. Theresultant residue was purified by chromatography on a silica gel column(diameter of 22 mm and height of 25 cm) as eluted with chloroform firstand then with a mixture (50:1) of chloroform and methanol. The5-O-(methylthio)thiocarbonyl derivative of said compound (VIIIa) (123mg) was obtained. FD-MS m/z 1297(M+H)⁺.

The 5-O-(methylthio)thiocarbonyl derivative (180 mg) was dissolved intoluene (4 ml), to which were then added tributyltin hydride (0.18 ml)and α,α-azobisisobutyronitrile (5 mg), and the mixture was heated at110° C. in argon stream for 50 minutes to effect the reaction intended.Hexane was added to the reaction solution obtained and the precipitateas deposited was separated centrifugally and then purified bychromatography on a silica gel column (diameter of 16 mm and height of17 cm) as eluted with chloroform first and then with a mixture (50:1) ofchloroform and methanol. The titled compound (154 mg) was afforded.FD-MS m/z 1191(M⁺) [α]_(D) ²⁰ +37° (c 1.3, CHCl₃).

(2)2"-Amino-4",6"-O-benzylidene-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-5,2"-dideoxydibekacin(Compound XIIIa):

The compound (149 mg) obtained in the above item (1) was,dissolved in amixture (1:19) of 88% formic acid and methanol (11.2 ml), and theresulting solution was subjected to hydrogenolysis (for 2.5 hours) in anargon atmosphere in the presence of a 10% palladium-carbon (520 mg) toremove the benzyloxycarbonyl groups from the 1- and 3"-amino groups. Thereaction solution obtained was filtered and the filtrate wasconcentrated to dryness, yielding the titled compound (96 mg). FD-MS m/z923(M+H)⁺.

(3) 2"-Amino-5,2"-dideoxyarbekacin (Compound Ib):

The compound (93 mg) obtained in the above item (2) was dissolved in THF(3 ml), to which was then added triethylamine (15 μl). To the solutionobtained was added a solution of an active ester which was prepared byadding N-hydroxysuccinimide (15 mg) and dicyclohexylcarbodiimide (28 mg)to 4-(p-methoxybenzyloxycarbonylamino)-2-hydroxybutyric acid (37 mg) inTHF (1.2 ml). The resulting reaction mixture was agitated at -15°-20° C.overnight to conduct the reaction and was filtered to remove a smallamount of insoluble matters. The filtrate was concentrated to dryness.The residue obtained was dissolved in chloroform (6 ml) and the solutionwas washed with a saturated aqueous sodium hydrogen carbonate solution(2 ml) and a 10% aqueous sodium chloride solution (2 ml), in order, andconcentrated to dryness. The resultant residue (100 mg) was thenpurified by chromatography on a silica gel column (diameter of 16 mm andheight of 25 cm) as eluted with a mixture of chloroform and methanol(30:1). There was afforded1-N-[(S)-4-(p-methoxybenzyloxycarbonylamino)-2-hydroxybutyryl]-2"-amino-4",6"-O-benzylidene-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-5,2"-dideoxydibekacin(Compound XIVa) (81 mg) as the 1-N-acylated product.

The compound thus obtained was dissolved in trifluoroacetic acid (1.8ml) and the solution was allowed to stand at room temperature for 1hour. The resulting reaction solution was concentrated to dryness andthen the residue was washed with ethyl ether (9 ml). The washed residuewas dissolved in a small amount of water, and the aqueous solution waspassed through a column of Amberlite CG-50 (NH₄ +form, 18 ml) forpurification. The column was then washed with water (40 ml) and elutedgradiently with 0.1˜1.5M aqueous ammonia. 2"-Amino-5,2"-dideoxyarbekacin(27 mg) was obtained as the object product.

EXAMPLE 3 Synthesis of 2"-amino-2"-deoxydibekacin (Compound IIa)

2"-Amino-4",6"-O-benzylidene-3,2',6',2"-N-tetrakis(t-butoxycabonyl)-2"-deoxydibekacin(Compound IXa) (38 mg) as described in EXAMPLE 1 (3) above wasdeprotected by treating with a 90% trifluoroacetic acid in the samemanner as in EXAMPLE 1 (4) above, and the deprotected product waspurified by chromatography on a column of Amberlite CG-50.2"-Amino-2"-deoxydibekacin (16 mg) was obtained as the object product.

EXAMPLE 4 Synthesis of 2"-amino-5,2"-dideoxydibekacin (Compound IIb )

2"-Amino-4",6"-O-benzylidene-3,2',6',2"-N-tetrakis(t-butoxycarbonyl)-5,2"-dideoxydibekacin(Compound XIIIa) (61 mg) as described in EXAMPLE 2 (2) above wasdeprotected by treating with a 90% trifluoroacetic acid in the samemanner as in EXAMPLE 1 (4) above, and the unprotected product waspurified by chromatography on a column of Amberlite CG-50.2"-Amino-5,2"-dideoxydibekacin (21 mg) was obtained as the objectproduct.

The seventh to ninth aspects of this invention are now illustrated withreference to the following Examples 5-6 to which this invention is notlimited.

EXAMPLE 5 Synthesis of 2"-amino-5,2"-dedeoxy-5-epi-fluoroarbekacin(Compound XVIa)

(1) Production of4",6",2'"-tri-O-acetyl-3,2',6',2",3",4'"-N-hexakis(t-butoxycarbonyl)-2"-amino-2"-deoxyarbekacin(Compound XVIIa-1):

2"-Amino-2"-deoxyarbekacin (400 mg) (Compound Ia) as prepared in EXAMPLE1 above was dissolved in a mixture of water (4 ml), methanol (6 ml) anddioxane (1 ml), and to the resulting solution were added triethylamine(0.1 ml) and di-t-butyl dicarbonate (1.2 ml), followed by agitating theresultant mixture at 35° C. for 26 hours. The reaction solution obtainedwas concentrated under reduced pressure to dryness, and the residue wasdissolved in pyridine (12 ml) to which acetic anhydride (2.4 ml) wasthen added under ice-cooling. The mixture obtained was agitated at roomtemperature for 3 hours and the resultant reaction solution containingthe titled compound formed was added with water (0.5 ml) and thenconcentrated under reduced pressure to dryness. The residue wasdissolved in chloroform (60 ml) and the solution obtained was washedthree times with 12 ml-portions of a 5% aqueous sodium hydrogencarbonate solution and once with 12 ml of a 10% aqueous sodium chloridesolution.

The washed solution in chloroform was dried over anhydrous sodiumsulfate and concentrated under reduced pressure. The concentrateobtained was purified by chromatography on a silica gel column asdeveloped first with chloroform and then with chloroform-methanol(40:1). Thus, there was afforded4",6",2'"-tri-O-acetyl-3,2',6',2",3",4'"-N-hexakis(t-butoxycarbonyl)-2"-amino-2"-deoxyarbekacin(Compound XVIIa-1) (840 mg. FD-MS m/z 1277(M⁺), [α]_(D) ²⁰ 41° (c 1.3,CHCl₃).

(2) Production of4",6",2'"-tri-O-acetyl-3,2',6',2",3",-4'"-N-hexakis(t-butoxycarbonyl)-2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin(Compound XVIIIa-1):

A solution in dichloromethane (3 ml) of Compound (XVIIa-1) (160 mg)obtained in the above item (1) was added into a solution ofdiethylaminosulfur trifluoride (0.078 ml) in a mixture ofdichloromethane (2.4 ml) and pyridine (0.16 ml) under ice-cooling. Themixture so obtained was subsequently stirred at room temperature for 2hours. The resulting reaction solution containing the titled compound asproduced was added with chloroform (4 ml) and then washed twice with 2ml-portions of a saturated aqueous sodium hydrogen carbonate solution,once with 2 ml of a 5% aqueous sodium hydrogen sulfate solution and thenonce with 2 ml of water.

The washed solution in the organic solvents was dried over anhydroussodium sulfate and concentrated under reduced pressure, and the residueobtained was purified by chromatography on a silica gel column asdeveloped first with chloroform and then with chloroform-acetone (4:1),to afford the titled compound (119 mg). FD-MS m/z 1280 (M+H)⁺, [α]_(D)²⁰ +29° (c 1.2, CHCl₃). (

3) Production of 2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin (CompoundXVIa):

The compound (120 mg) obtained in the above item (2) was dissolved inmethanol (1.8 ml), to which was then added 1N sodium methylate inmethanol (0,068 ml). The mixture obtained was stirred at roomtemperature for 1 hour, and the resulting reaction solution wasneutralized by addition of a cation-exchange resin, Dowex 50W (H⁺ form)and then concentrated under reduced pressure. To the residue obtainedwas added 90% trifluoroacetic acid (1 ml) under ice-cooling, followed bystirring the mixture for 1.5 hours.

The resulting reaction solution contained the above titled compoundproduced as the unprotected product. This reaction solution wasconcentrated under reduced pressure and the concentrated solution wasmixed with water (1 ml), followed by concentrating the mixture todryness. The solid residue was taken up into water (3 ml) and theaqueous solution obtained was washed three times with 0.6 ml-portions ofchloroform. The aqueous phase so washed was concentrated under reducedpressure and then the concentrate was charged into a cation-exchangeresin, Amberlite CG-50 (NH₄ ⁺ form, 10 ml) for adsoption of the titledcompound by the resin. The resin column was then washed with water (20ml) and then subjected to gradient elution with 0.2M to 0.8M aqueousammonia for isolation and purification of the titled compound.2"-Amino-5,2"-dideoxy-5-epi-fluoroarbekacin (Compound XVIa) was obtainedin a yield of 27 mg.

EXAMPLE 6 Synthesis of 2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin(Compound XVIb)

(1) Production of4",6",2'"-tri-O-acetyl-3,2',6',2",3",-4'"-N-hexakis(t-butoxycarbonyl)-2"-amino-5,2"-dideoxy-5-epi-azidoarbekacin(Compound XVIIIb-1):

4",6",2'"-tri-O-acetyl-3,2',6',2",3",4'"-N-hexakis(t-butoxycarbonyl)-2"-amino-2"-deoxyarbekacin(Compound XVIIa-1) (235 mg) as obtained in EXAMPLE 5 (1) above wasdissolved in dichloromethane (10 ml), to which was then addeddimethylaminopyridine (674 mg) and further added methanesulfonylchloride (0.214 ml) under ice-cooling. The mixture so obtained wasstirred at room temperature for 16 hours to effect the mesylation. Afterthis reaction, the resulting reaction solution was mixed with chloroform(15 ml), followed by washing three times with 5 ml-portions of a 5%aqueous potassium hydrogen sulfate solution and once with a 10% aqueoussodium chloride solution. The washed organic phase was dried overanhydrous sodium sulfate and then concentrated under reduced pressure.

The residue obtained was dissolved in dimethylformamide (4.8 ml), and tothe resulting solution was added sodium azide (127 mg). The mixtureobtained was heated at 120° C. for 3 hours under agitation. Theresulting reaction solution containing the above titled compound asproduced was concentrated under reduced pressure, and the residue wasdissolved in chloroform (25 ml). The solution obtained was washed threetimes with 5 ml-portions of a 10% aqueous sodium chloride solution andthe washed organic phase in chloroform was then dried over anhydroussodium sulfate and concentrated under reduced pressure. The resultingresidue was purified by chromatography on a silica gel column asdeveloped first with chloroform and then with chloroform-methanol(10:1), so that the titled compound (233 mg) was afforded. FD-MS m/z1303(M+H)⁺, [α]_(D) ²⁰ +33° (c 1.1, CHCl₃).

(2) Production of4",6",2'"-tri-O-acetyl-3,2',6',2",3",4'"-N-hexakis(t-butoxycarbonyl)-2"-amino-5,2"-dideoxy-5-epi-aminoarbekacin(Compound XVIIIc-1):

The compound (140 mg) obtained in the above item (1), namely Compound(XVIIIb-1), was dissolved in methanol (6 ml) and then subjected tohydrogenation under a normal pressure for 3 hours in the presence ofRanney-nickel as catalyst. The resulting reaction solution was-filteredto remove the catalyst, and the filtrate was concentrated under reducedpressure. The residue obtained was purified by chromatography on asilica gel column as developed first with chloroform-acetone (4:1) andthen with chloroform-methanol (20:1), so that the above titled compound(89 mg) was obtained. FD-MS m/z 1277(M+H)⁺, [α]_(D) ²⁰ 43° (c 1.1,CHCl₃).

(3) Production of 2"-amino-5,2"-dideoxy-5-epi-amino-arbekacin (CompoundXVIb):

The compound (87 mg) obtained in the above item (2), namely Compound(XVIIIc-1), was dissolved in methanol (1.8 ml) and then subjected to thedeprotecting treatments with sodium methylate and with trifluoroaceticacid in the same manner as in the above procedures of EXAMPLE 5 (3)above. The unprotected product so obtained was purified bychromatography on a column of Amberlite CG-50 resin (NH₄ ⁺ form, 10 ml)to give the above titled compound (Compound XVIb), namely2"-amino-5,2"-dideoxy-5-epi-amino-arbekacin (28 mg).

We claim:
 1. 2"-Amino-2"-deoxyarbekacin having the formula ##STR45## ora pharmaceutically acceptable acid addition salt thereof. 2.2"-Amino-2"-deoxydibekacin having the formula ##STR46## or apharmaceutically acceptable acid addition salt thereof. 3.2"-Amino-5,2"-dideoxy-5-epi-fluoroarbekacin having the formula ##STR47##or a pharmaceutically acceptable acid addition salt thereof.
 4. Anantibacterial composition comprising an antibacterially effective amountof 2"-amino-2"-deoxyarbekacin according to claim 1 or a pharmaceuticallyacid addition salt thereof as active ingredient, in combination with apharmaceutically acceptable carrier for the active ingredient.
 5. Anantibacterial composition comprising an antibacterially effective amountof 2"-amino-2"-deoxydibekacin according to claim 2 or a pharmaceuticallyacid addition salt thereof as active ingredient, in combination with apharmaceutically acceptable carrier for the active ingredient.
 6. Anantibacterial composition comprising an antibacterially effective amountof 2"-amino-5,2"-dideoxy-5-epi-fluoroarbekacin according to claim 3 or apharmaceutically acid addition salt thereof as active ingredient, incombination with a pharmaceutically acceptable carrier for the activeingredient.
 7. A process for the-preparation of2"-amino-2"-deoxyarbekacin of the following formula (Ia) ##STR48## whichcomprises the steps of: protecting each of the 1- and 3"-amino groups of3,2',6'-N-tris(alkoxycarbonyl)-dibekacin represented by general formula(III) ##STR49## wherein A means an alkoxycarbonyl group serving as anamino-protecting group removable by hydrolysis, with anaralkyloxycarbonyl group which is an amino-protecting group removable byhydrogenolysis, to form a 1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'-N-tris(alkoxycarbonyl)-dibekacin represented by general formula (IV) ##STR50##wherein A has the meaning as defined above and B means anaralkyloxycarbonyl group;protecting both of the two hydroxyl groups atthe 4"- and 6"-positions of the compound of general formula (IV) with anaralkylidene or alkylidene group as a hydroxyl-protecting group, to forma 4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'-N-tris-(alkoxycarbonyl)-dibekacinrepresented by the following formula (V) ##STR51## wherein A and B havethe meanings as defined above and Y means an aralkylidene or alkylidenegroup; oxidizing the 2"-hydroxyl group of the compound of formula (V)with an oxidizing agent to form a 4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2'-6'-N-tris(alkoxycarbonyl)-2"-deoxy-2"-oxodibekacin represented by the followingformula (VI) ##STR52## wherein A, B and Y have the meanings as definedabove; converting the 2"-oxo group of the compound of formula (VI) into2"-amino group by reducing the same with a hydride in the presence ofammonium acetate, thereby to form a 2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6'-N-tris(alkoxycarbonyl)-2-deoxydibekacinrepresented by the following formula (VII) ##STR53## wherein A, B and Yhave the meanings as defined above; protecting the 2"-amino group of thecompound of formula (VII) with an alkoxycarbonyl group (A) to form a2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacin represented by the following formula(VIII) ##STR54## wherein A, B and Y have the meanings as defined above;eliminating the aralkyloxycarbonyl groups (B) from the 1- and 3"-aminogroups by hydrogenolysis to form a 2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacinrepresented by the following formula (IX) ##STR55## wherein A and Y havethe meanings as defined above; acylating the 1- amino group of thecompound of formula (IX) with an active ester or acid halide of(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonylamino)-2-hydroxybutyric acid represented by the followingformula (X) ##STR56## wherein A' means ap-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group as anamino-protecting group removable by hydrolysis, to form a1-N-[(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonyl-amino)-2-hydroxybutyryl]-2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis (alkoxycarbonyl)-2"-deoxydibekacinrepresented by the following formula (XI) ##STR57## wherein A, Y and A'have the meanings as defined above; and hydrolyzing the compound offormula (XI) to remove therefrom the alkoxycarbonyl group (A), thep-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group (A'), andthe aralkylidene or alkylidene group (Y) and to produce the compound offormula (Ia).
 8. A process for the preparation of2"-amino-5,2"-dideoxyarbekacin of the following formula (Ib) ##STR58##which comprises the steps of: eliminating by a known deoxygenationmethod the 5-hydroxyl group of a 2"-amino-4",6"-O-aralkylidene oralkylidene1,3"-N-bis(aralkyloxycarbonyl)-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxyydibekacinrepresented by general formula (VIII) ##STR59## wherein A means analkoxycarbonyl group, B means an aralkyloxycarbonyl group and Y means anaralkylidene or alkylidene group, to form a2"-amino-4",6"-O-aralkylidene oralkylidene-1,3"-N-bis(aralkyloxycarbonyl)-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacin represented by the followingformula (XII) ##STR60## wherein A, B and Y have the meanings as definedabove; eliminating the aralkyloxycarbonyl groups (B) from the 1- and3"-amino groups of the compound of formula (XII) to form a2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacinrepresented by the following formula (XIII) ##STR61## wherein A and Yhave the meanings as defined above; acylating the 1- amino group of thecompound of formula (XIII) with an active ester or acid halide of(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonylamino)-2-hydroxybutyric acid represented by the followingformula (X): ##STR62## wherein A' means ap-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group as anamino-protecting group removable by hydrolysis, to form a1-N-[(S)-4-(p-alkoxy-substituted-benzyloxycarbonyl- oralkoxycarbonyl-amino)-2-hydroxybutyryl]-2"-amino-4",6"-O-aralkylidene oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-5,2"-dideoxydibekacinrepresented by the following formula (XIV) ##STR63## wherein A, Y and A'have the meanings as defined above; and hydrolyzing the compound offormula (XIV) to remove therefrom the alkoxycarbonyl group (A), thep-alkoxy-substituted-benzyloxycarbonyl or alkoxycarbonyl group (A'), andthe aralkylidene or alkylidene group (Y) and to produce the compound offormula (Ib).
 9. A process for the preparation of2"-amino-2"-deoxydibekacin of formula (IIa) ##STR64## which comprisesremoving9 the aralkylidene or alkalidens group (Y) and alkoxycarbonylgroup (A) of a 2"-amino-4", 6"-O-aralkylidene-oralkylidene-3,2',6',2"-N-tetrakis(alkoxycarbonyl)-2"-deoxydibekacinrepresented by general formula (IX): ##STR65## wherein A means analkoxycarbonyl group and Y means an aralkylidene or alkylidene group,from the compound of formula (IX) to produce the compound of formula(IIa).